In the power generation and distribution industry, utility companies generate and distribute electricity to their customers. To facilitate the process of distributing electricity, various types of power switching devices are used. In a distribution circuit, electricity flows through the power switching devices from a power generation source (typically a substation or the like) to the consumer. When a fault is detected in the distribution circuit, the power switching device is opened and the electrical connection is broken.
Controllers are used by the utility company to detect faults that occur in the distribution circuit. Controllers typically use a microprocessor or microcontroller programmed to respond to the fault based on the type of fault, the type of power switching device connected to the controller, and the location of the fault. The controller may respond to a particular fault by causing the power switching device to remain open. Alternatively, upon detection of a fault, the controller may cause the power switching device to open and close multiple times.
Faults typically occur when excess amounts of electrical current are conducted through the distribution circuit. The controller is programmed to detect when fault conditions occur and respond with a preprogrammed response. The distribution circuit generally has several power switching devices connected in series, cascaded from a substation to the consumer. When a fault occurs in the distribution circuit, it is important that the controller closest to the fault isolate the fault. This allows the least number of customers to be affected by the fault.
Utility companies typically coordinate the responses of the power switching devices to isolate any faults with minimal service interruption. To accomplish this, the responses of the cascaded power switching devices are coordinated so the controller closest to the fault detects the fault condition and causes its associated power switching device to open. When the power switching device opens, the flow of electricity is interrupted.
A power switching device may have a delay in responding to a fault condition. Therefore, in programming the response of cascaded power switching devices to a fault condition, the utility company should take into account the response delay of each power switching device in the cascade. Taking that delay into account will give the controller closest to the fault enough time to analyze and detect the fault condition and cause its associated power switching device to respond before a controller at a higher level in the cascaded network responds to the fault.
As is common in the industry, utility company personnel use overcurrent response curves (also referred to as protection curves) to predict the amount of time it takes for a power switching device to open after a fault condition is detected. To configure the cascading power switching devices, the response times of the power switching devices must be accurately modeled. Part of the modeling process requires that an estimated range of response times be taken into account. A fault response tolerance is a value that is added to or subtracted from the predicted fault response time to allow for any deviation in the actual response time. Typically, utility companies provide guidelines to their employees outlining how to calculate the fault response tolerances for the power switching devices. For example, one utility may determine that the measured value of fault current may deviate by a predetermined percentage. Using the overcurrent response curves and plotting the range of values for the fault current, the utility company personnel can predict the fault response tolerances based on this range. The power switching devices are then configured based on the fault response tolerance results.
One drawback with existing configuration tools used to program the power switching devices is the lack of an automated fault response tolerance calculation tool. Utility company personnel currently utilize a manual method of calculating overcurrent response tolerances when configuring the power switching devices. This process is time consuming and subject to human error.
One alternative to the manual calculation method is the use of a fault response tolerance calculation tool. However, existing fault response tolerance calculation software tools are offered as a separate software package by third party vendors not associated with the vendors of the configuration software tool used to configure the controllers. Thus, the utility company personnel may need two separate computer systems, one for configuring and the other for fault response tolerance calculations.
The present invention improves both the efficiency and accuracy of configuring power switching devices in a power distribution network. The present invention provides a fault response tolerance calculation tool as part of the configuration tool used to configure the power switching devices in the power distribution network. The present invention uses software located in the user interface to calculate the fault response tolerances and display the adjusted fault response times for a given power switching device for a given set of parameters. The utility company employee is able to alter the configuration of the power switching device based on the adjusted fault responses. After altering the configuration of the power switching device, the present invention allows the utility company personnel to recalculate the fault response tolerances and confirm that the configuration settings conform to utility company guidelines. By integrating the two tools together, the present invention improves both the accuracy and efficiency of the configuration process because utility company personnel do not have to transition between two separate software tools when configuring power switching devices.